The present invention relates to a system and a method for cooling a fuel cell system installed on board an aircraft.
Fuel cell systems enable low-emission, highly efficient generation of electric current. For this reason, efforts are currently being made to use fuel cell systems to generate electrical energy in various mobile applications, such as for example in automotive engineering, in shipping or in aviation. It is, for example, conceivable in an aircraft to replace the generators, which are currently used to supply power on board and are driven by the main engines or the auxiliary turbine, with a fuel cell system. A fuel cell system, moreover, could also be used to supply the aircraft with emergency power and replace the ram air turbine hitherto used as an emergency power system. Besides electrical energy, a fuel cell during operation generates thermal energy, which has to be removed from the fuel cell with the aid of a cooling system in order to prevent overheating of the fuel cell. A fuel cell used in an aircraft, for example for the on-board power supply, has to be designed in such a way that it is capable of meeting the demand for electrical energy. However, a fuel cell that has a high capacity with regard to generating electrical energy, also generates, due to the efficiency, corresponding thermal energy, and therefore has a corresponding cooling requirement.
In principle, a fuel cell system used on board an aircraft can be cooled in various ways. For example, DE 10 2009 013 159 A1 or WO 2010/105744 A2 describes a cooler which is integrated into an outer skin of the aircraft and through which ambient air can flow in order to remove waste heat generated by a fuel cell system to the aircraft surroundings.
By contrast, DE 10 2009 048 394 A1 proposes coupling a cooling circuit, which removes thermal energy generated by a fuel cell system during operation from the fuel cell system, thermally to a fuel tank, in order to utilize fuel held in the fuel tank as a heat sink for cooling the fuel cell system.
Finally, from DE 10 2007 060 428 B3 or WO 2009/077048 A1 there is known an evaporative cooling system for cooling a fuel cell system, in which a cooling medium is converted from the liquid to the gaseous state of matter by the thermal energy generated during operation of the fuel cell system.